| Complete Conversions Ltd | Construction | 2011 |
| Complete Electrical Engineering Ltd | Construction | 2025 |
| Complete Engineering Services Ltd | Professional & scientific | 2024 |
| Complete House Clearance Ltd | Transport & logistics | 2026 |
| Complete Industrial Supplies Ltd | Wholesale & retail | 2020 |
| Complete Office Solutions (WG) Ltd | Wholesale & retail | 2009 |
| Complete Package Recruitment Ltd | Administrative & support | 2019 |
| Complete Property Renovations Services Ltd | Construction | 2023 |
| Complete Retail Security Limited | Administrative & support | 2009 |
| Complete Rugby Project Ltd | Education | 2020 |
| Complete Solution Services Limited | Professional & scientific | 2018 |
| Complete Window Services Ltd | Construction | 2024 |
| Complex Care MK1 Ltd | Health & social care | 2026 |
| Complex Computers Ltd | Wholesale & retail | 2019 |
| Compliance Auditing Technology Ltd | Information & communication | 2021 |
| Compliance Health Limited | Public administration | 2018 |
| Compliance Hub Contractors Limited | Professional & scientific | 2014 |
| Compliance Hub Limited | Professional & scientific | 2009 |
| Compliance Passport Limited | Administrative & support | 2025 |
| Compliance Passport Service Limited | Administrative & support | 2025 |
| Compliance POD Limited | Information & communication | 2019 |
| Compose IT Limited | Information & communication | 2010 |
| Composite Board Ltd | Professional & scientific | 2020 |
| Compound Coaching Ltd | Arts & recreation | 2023 |
| Computer Terrorism (UK) Ltd | Information & communication | 2004 |
| Computers by Post Limited | Extraterritorial | 1996 |
| Comrock Records Ltd | Information & communication | 2019 |
| Comtrad Tech Ltd | Manufacturing | 2021 |
| Conash Consulting Limited | Information & communication | 2023 |
| Conceit Limited | Hospitality | 2021 |
| Concentrix Medica UK Ltd | Health & social care | 2022 |
| Concentrix UK Holdings Ltd | Information & communication | 2012 |
| Concentrix UK Trading Ltd | Information & communication | 2012 |
| Concept 73 Developments Ltd | Construction | 2019 |
| Concept by Design Limited | Wholesale & retail | 2023 |
| Concept Copiers Direct Limited | Administrative & support | 2019 |
| Concept GSM Ltd | Information & communication | 2007 |
| Concept IDL LLP | | 2013 |
| Concept Interiors Ltd | Wholesale & retail | 2015 |
| Concept Investments Limited | Administrative & support | 2003 |
| Concept Wealth Ltd | Financial services | 2020 |
| Concerteenies | Education | 2022 |
| Concha Limited | Hospitality | 2022 |
| Conco SV Ltd | Manufacturing | 2021 |
| Concorde SY Ltd | Hospitality | 2023 |
| Concordia Financial Planning Ltd | Financial services | 2023 |
| Concordia Salus Limited | Health & social care | 2024 |
| Concrete Canvas Boxing Gym CIC | Education | 2025 |
| Concrete Wall Club Limited | Professional & scientific | 2023 |
| Conduit Group Ltd | Hospitality | 2023 |
| Condurache Construction Ltd | Construction | 2026 |
| Coneing and Traffic Flow Ltd | Transport & logistics | 2015 |
| Confederation of Dental Employers Ltd | Health & social care | 1983 |
| Confidence Aesthetics Ltd | Other services | 2026 |
| Confidence Digital Ltd | Administrative & support | 2021 |
| Confidental Health Ltd | Health & social care | 2015 |
| Confidental Holdings Ltd | Health & social care | 2025 |
| Confined Space Rescue Limited | Extraterritorial | 2018 |
| Conflict Resolution Education in Sheffield Schools Training | Education | 2006 |
| Confurr Ltd | Information & communication | 2020 |
| Conkai Security Limited | Other services | 2010 |
| Conlon Repair Solutions Limited | Manufacturing | 2025 |
| Connect 2 Float Ltd | Health & social care | 2023 |
| Connect Financial Mortgages Limited | Financial services | 2015 |
| Connect Financial Solutions Limited | Financial services | 2014 |
| Connect International Limited | Transport & logistics | 2023 |
| Connect Medical Agency Ltd | Administrative & support | 2014 |
| Connect+Plumbing and Heating Ltd | Construction | 2025 |
| Connect-Ip Ltd | Information & communication | 2005 |
| Connected Medtech Limited | Professional & scientific | 2025 |
| Connected Plumbing & Heating Limited | Construction | 2017 |
| Connected Renovations & Maintenance Ltd | Construction | 2022 |
| Connected Search Group Holdings Limited | Financial services | 2026 |
| Connected Search Group Ltd | Professional & scientific | 2023 |
| Connecting Paths C.I.C. | Education | 2025 |
| Connecting People Consultancy Limited | Professional & scientific | 2019 |
| Connection Products Limited | Administrative & support | 2005 |
| Connections Contact Services Ltd | Health & social care | 2024 |
| Connections Housing CIC | Administrative & support | 2019 |
| Connections in Learning Limited | Education | 2012 |
| Connector Publishing Ltd | Information & communication | 2025 |
| Connectrical Ltd | Construction | 2023 |
| Connie’S Haven Limited | Health & social care | 2022 |
| Connor Fell Ltd | Construction | 2024 |
| Connor Ryan Limited | Financial services | 2018 |
| Conquerors Commercial Goods and Services Ltd | Wholesale & retail | 2022 |
| Conroy Barnes Ltd | Real estate | 2025 |
| Conscious Investments Limited | Real estate | 2024 |
| Consecrated Construction Marketing Ltd | Professional & scientific | 2024 |
| Conserv Services Limited | Hospitality | 2025 |
| Consilient Consulting Limited | Professional & scientific | 2006 |
| Consolidated Assets Limited | Real estate | 2009 |
| Consolidated Fuzz Limited | Arts & recreation | 2014 |
| Consone Quartet LLP | | 2021 |
| Consortium Drilling Limited | Mining & quarrying | 2021 |
| Constance Grant Dance Centre Limited | Education | 2013 |
| Constantine Roofing Ltd | Construction | 2017 |
| Constellation Lighting Limited | Manufacturing | 2004 |
| Construct & Design UK Ltd | Construction | 2019 |
| Construction & Consultancy (Yorkshire) Ltd | Professional & scientific | 2026 |